1. Field of the Invention
The present invention relates to biochemical processing apparatus for biochemically processing analytes, and particularly to a DNA testing apparatus including sections for amplifying and purifying DNA analytes.
2. Description of the Related Art
In order to rapidly and accurately analyze nucleotide sequences or to detect a target nucleic acid in a nucleic acid sample, many approaches have been proposed which use hybridization reactions with probe carriers, such as DNA microarrays. The DNA microarray includes probes having nucleotide sequences that may be complementary to a target nucleic acid and the probes are closely fixed on a solid phase, such as beads or a glass plate. In general, the target nucleic acid is detected through the following steps.
First, a target nucleic acid is extracted from a living body sample, such as blood or urine.
In the second step, the extracted target nucleic acid is amplified by, for example, the PCR (polymerase chain reaction) method. More specifically, a first and a second primer are added to a nucleic acid sample, and the sample is subjected to a thermal cycle in the presence of an enzyme. The first primer is specifically bound to part of the target nucleic acid, and the second primer is specifically bound to part of the complementary nucleic acid to the target nucleic acid. If a double-stranded nucleic acid containing the target nucleic acid is bound with the first and second primers, the double-stranded nucleic acid is amplified by elongation (hereinafter referred to as the first PCR).
After the double-stranded nucleic acid containing the target nucleic acid is sufficiently amplified, components other than the amplified double-stranded nucleic acid, such as unreacted primers and nucleic acid fragments, are removed by purification. For the purification, some techniques have been known. For example, the double-stranded nucleic acid may be adsorbed to magnetic particles, or a column filter may be used.
Then, a third primer is added to the purified nucleic acid sample, followed by a thermal cycle. The third primer has been labeled with an enzyme, a fluorescent or luminescent material, or the like, and is specifically bound to part of the complementary nucleic acid to the target nucleic acid. If the complementary nucleic acid to the target nucleic acid is bound to the third primer, a labeled target nucleic acid is amplified by elongation (hereinafter referred to as the second PCR).
If the nucleic acid sample contains the target nucleic acid, the labeled target nucleic acid is produced. If the nucleic acid sample does not contain the target nucleic acid, the labeled target nucleic acid is not produced.
The nucleic acid sample is brought into contact with a DNA microarray so as to hybridize with the probes in the DNA microarray. If the target nucleic acid complementary to a probe is present, the probe and the target nucleic acid hybridize.
In the third step, the target nucleic acid is detected. The label of the target nucleic acid tells whether the probe has hybridized with the target nucleic acid. Thus, it can be determined whether a specific nucleotide sequence is present or absent.
Japanese Patent Laid-Open No. 7-107999 has disclosed an apparatus for continuously performing these steps. The apparatus includes a movable dispenser that transfers a desired liquid into a container so that a reaction occurs.
Reagents used in biochemical reactors often have to be intentionally prevented from deteriorating. In particular, enzymes important for biochemical reaction may deteriorate at room temperature, and are generally stored at a predetermined temperature or less. If such reagents are used in a limited space in a reactor, a cold storage section for storing the reagents and a reaction section must be closely disposed. Unfortunately, for amplification, the reaction section is subjected to a thermal cycle between about 55° C. and 95° C. If the reaction section is close to the cold storage section, the temperature of the thermal cycle may be conducted to the cold storage section. Furthermore, purification after the amplification may be disadvantageously performed in a limited space.
The apparatus disclosed in Japanese Patent Laid-Open No. 7-107999 includes a purifying section on the left side, a heating section in the middle, and a cold storage section on the right side when viewed from above, and a container is transferred from one section to another. This arrangement increases the width of the apparatus and requires the container to move a long distance, because these sections are apart from each other. Accordingly, it takes a longer time to test.